The development apparatus, which is mounted in an image-forming device, is often equipped with a sealing member for preventing toner leaks, the member sliding on each end of the developing roller so that the toner is prevented from leaking to the outside of the development apparatus, so that the development apparatus, the image-forming device and recording materials are kept from stains. Nevertheless, the toner sometimes leaks from around the ends of the developing roller. The leakage of the toner notably occurs especially in high-temperature and high-humidity environments.
Some techniques to address this problem have been proposed. For example, patent document 1 discloses “a single-component development apparatus comprising a toner container for containing a toner; a toner carrier, which is rotatably supported at an opening of the toner container, for carrying and conveying the toner; a supplying roller for supplying the toner to the toner carrier; and a toner-controlling member, which contacts the developing roller, for controlling the toner that is carried and conveyed by the toner carrier, wherein the development apparatus has a metal shaft coated with resin, and the axial extent of the resin-coated area of the toner carrier is limited within sealing members placed on both ends of the toner carrier”.
Also, patent document 2 discloses “a developing roller for an electrographic printer, which carries toner on an outer circumferential face of the roller, comprising a roller member held so as to be rotatable; a conductive member made of a conductive material, which is placed in the development area of the circumferential face of the roller member and carries toner thereon; and a non-conductive member made of a non-conductive material, which is placed on an end of the conductive member and prevents adherence of the toner”.
In addition to the prevention of the leakage of toner, the development apparatus is required to form high quality images. For example, patent document 3 specifically teaches “a developing roller comprising a base layer including silicone polymer and 1-hexyl-3-methylimidazolium trifluoromethanesulfonate” to prevent image irregularities (Working Example 16).